Multicomponent fibers are, in and of themselves, well known and have been used extensively to achieve various fiber properties. For example, multicomponent fibers have been formed of two dissimilar polymers so as to impart self-crimping properties. See, U.S. Pat. No. 3,718,534 to Okamoto et al and U.S. Pat. No. 4,439,487 to Jennings. Multicomponent fibers of two materials having disparate melting points for forming point bonded nonwovens are known, for example, from U.S. Pat. No. 4,732,809 to Harris et al. Asymmetric nylon-nylon sheath-core multicomponent fibers are known from U.S. Pat. No. 4,069,363 to Seagraves et al.
One problem that is encountered when multicomponent fibers are formed having distinct domains of dissimilar polymers which are incompatible with one another is that the domains often separate at the boudary between the domains. This separation results in fracturing or splitting of the fiber thereby weaking the system (e.g., yarn, fabric, carpet or like textile product) in which the fiber is used. Weakening of the fiber system can be sufficiently acute to prevent the system from undergoing downstream processing (e.g., drawing, texturing, heat-setting, tufting, knitting, weaving and the like). Furthermore, such fracturing and/or splitting of the fibers can result in poor product qualities such as poor appearance and poor wear performance.
It would therefore be higly desireable if multicomponent fibers having distinct longitudinally coextensive polymer domains formed of incompatible polymers could be produced which have minimal (if any) inter-domain fracturing and/or splitting. It is towards providing such a fiber and method of producing the same that the present invention is directed.
Broadly, the present invention is directed to a multicomponent fiber and a method of producing the same whereby the inter-domain boundary layer between the distinct domains is surface roughened and/or mechanically modified so as to increase the surface area contact (and thereby the adhesion) therebetween. As such, delamination of the domains at their interfacial boundary layer is minimized (if not eliminated entirely). Preferably, the fibers of this invention are concentric core-sheath bicomponent fibers whereby the core is surface roughened and/or mechanically modified so that of the inter-domain boundary layer between the core and the sheath appears in cross-section to have multiple circumferentially spaced-apart outwardly extending serrations, ribs and/or peaks.
These and other aspects and advantages of the present invention will become more clear after careful consideration is given to the detailed description of the preferred exemplary embodiments thereof which follow.